Primary open angle glaucoma (POAG) produces a subtantial reduction in human visual capacity which results from damge to the retinal ganglion cells caused by elevated introcular pressure. Measurement of the reduction in human visual capacity produced by glaucoma generally involves detection and quantification of visual field defects and optic disc abnormalities. These techniques are not presently appropriate for examining subtle, early changes in visual characteristics. However, these early changes in visual function need to be understood if the mechanisms involved in the reduction of visual capacity are to be fully elucidated. Electrical potentials generated in the human retina when phase-alternating patterns are viewed (pattern reversal retinal potentials) appear to represent the electrical activity of ganglion cells. Examination of any changes in the electrical activity which results from elevated intraocular pressure or glaucoma may, therefore, provide a sensitive index to the reduction in visual capacity. This proposal seeks support for research to quantitatively examine the effects of elevated intraocular pressure and/or glaucoma on the characteristics of pattern reversal retinal potentials.